A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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12 views

Test if two means are significantly different in R [duplicate]

I would like to test if two means are significantly different from each other. I am using R and I do this: t.test(SampleA,SampleB) and I get output that looks ...
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21 views

Dissertation-results section [on hold]

basically i am testing 2 species of pigs, 2 pigs of the same species in one enclosure and another 2 in a different enclosure, My aim is to see if alterations to feeding regimes have an effect on an ...
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1answer
15 views

Pre-post measurements with a control group

I am running a study looking at the effect of Vitamin C on muscle function. For my study design, I had 2 groups: A treatment (vit C) and a control (no treatment) group. Pre and post measurements were ...
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0answers
9 views

Performing t test, one-way ANOVA from mean and SD using SPSS

I have the following summarized data: Group 1: n=44, mean 12.1, SD 2.0 Group 2: n=56, mean 13.2, SD 2.5 Group 3: n=42, mean 12.7, SD 2.3 Is it possible to perform the t test comparing means of group ...
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1answer
34 views

Test if two gamma distributed populations are different

I have data from two populations of different sizes. Both have Gamma distributions with different shapes and scales (as estimated in r): fitdistr(x/10000, "gamma") #186 members shape 0.586219900 ...
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18 views

Comparing means between two groups if dependent variable is a percentage

I have data on recovery rates from several hospitals across the country. The recovery rates are in percentages. I want to compare the mean recovery rate between two groups of hospitals, one that uses ...
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0answers
17 views

Equivalent to Welch's t-test in GLS framework

How can Welch's t-test be expressed as a generalized least squares model? A standard independent samples t-test (where it is assumed that the samples being compared are drawn from populations with ...
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1answer
50 views

Size of Tukey's 1 Degree of Freedom Test

In Oehlert (p. 218) the following algorithm for computing Tukey's one degree of freedom test for non-additivity is suggested: Fit a preliminary model; this will usually be an additive model. ...
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1answer
57 views

simulate t-tests of mean differences

I would like to simulate t-tests of mean differences. I would like to simulate data based on 1) pre-specified (desired) mean difference between the variables and 2) desired t value 3) and p-value ...
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2answers
28 views

Should I use paired t-tests or ANOVA when comparing multiple variables from 2 tests?

I had 50 subjects perform two 30-minute cycling time trials on separate days. I would like to compare the means of several variables from each of the two tests: Cadence, Heart Rate, Power Output, and ...
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13 views

Concept of performing a t-test while controlling/adjusting for one or more variables? [duplicate]

Could someone please help me understand the concept of performing a t-test while controlling/adjusting for one or more variables? E.g.: Say I have a hypothetical data set, with the following ...
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1answer
19 views

Properly interpreting and presenting a differences in differences t-test in written and table forms

I have two separate groups of students. A control (n=23) and intervention (n=19) group. Both groups took a pre test measure (score of 0-100). I have done an independent t-test on the Post_minus_Pre ...
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1answer
23 views

Can I do a dependent t-test if pre & post were anonymous?

I am trying to analyze the following case study using SPSS. What I have done so far as part of my research is to conduct a case study to measure the affect the introduction of different technology ...
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26 views

Longitudinal pre-post test/follow up

I am an undergrad student trying to get my head around statistical analysis. Can someone help me to make sense of the best way to analyse my data? ANOVA, ANCOVA, t-tests....it is all a foreign ...
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1answer
54 views

Test for equality of lines, simple regression

I have two data sets with the same predictor and response and I want to obtain a p-value that they follow the same regression model $E(y)=ax+c$. Sample sizes are different. What test should I use? ...
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12 views

Formally stating hypotheses with two parts

I'm trying to state my hypotheses formally for my dissertation, but I'm getting my brain in a twist here. H0: (µ1- µ2) – (µ3- µ4) ≤ 0: The mean difference in response time between low load ...
2
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1answer
33 views

t-test, which version to use?

I have a very small data set, with two groups, 5 cases in each one. I ran the t-test, and got a p value of 0.049. The F test that SAS ran in addition gave a p value of 0.72. This is not a surprise, ...
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1answer
15 views

How should I present paired sample test results? [closed]

I conducted a paired sample t-test on pre and post questionnaire results. What should I be reporting?
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2answers
61 views

Calculate t-statistic step by step in R

Hello: I'm a faculty member teaching a stats class, and I'd like to show students how to calculate the t-statistic from an independent samples t-test (mostly) step-by-step. Using the code below, ...
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1answer
57 views

Effect of sample size in F-test?

Having worked hard to understand the t-test, I'm rapidly falling out of love with it. All that is required in the t-test to gain significance is increase sample size, which renders it close to ...
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5 views

Post-hoc test on 3 groups comparison

I have 3 groups each with 6 values. After performing acceptable levene test for Homogeneity of Variance, I performed Anova on my data. It was significant, and I started to perform post-hoc test. The ...
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0answers
36 views

Question about normality assumption of t-test

For t-tests, according to most texts there's an assumption that the population data is normally distributed. I don't see why that is. Doesn't a t-test only require that the sampling distribution of ...
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2answers
70 views

Help performing hypothesis tests automatically on a large data set in R

I have a data frame in R with 100 variables (columns) and 100 observations (rows). Each row is a patient; the columns are different variables such as gender, height, body-mass index, etc. I know that ...
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33 views

is it legitimate to t-test between statistics of a bootsrap?

say I have two samples $x_1$ and $x_2$ and a function which calculates a statistic out of each sample, denotes as $f(x)$. I would like to test the significance of the difference $f(x_1)-f(x_2)$. A ...
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2answers
32 views

Testing if distribution is similar between two groups

I have a variable young that is equal to 1 if a participant is less than 25 years old. I then have a list of of each ...
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22 views

Analyzing Proximity Pattern Data in Gorillas

I have a whole bunch of data about proximity patterns between 2 gorillas (distance in meters, taken during set time intervals). I'm interested in comparing the differences in proximity between the 2 ...
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23 views

Multiple t tests or an ANOVA?

I have low anxiety and high anxiety participants (21 in high anxiety and 20 In low). I measured anxiety and then categorised Pts according to this. They completed two memory tasks. In one memory ...
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1answer
84 views

How do you tell if you should use a one-tailed test or a two-tailed test in a t-test?

For example, how would you decide between which tailed test to do in the following experiment: Ethanol dilutions were made with different proportions and Daphnias were submerged in them to collect ...
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2answers
30 views

Cohen's d in non-significant results

I did several independend t-tests. Some of them are significant, some of them are not. Next, I computed Cohens $d$ for effect size. For significant results, Cohens $d$ feels intuitively reasonable ...
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1answer
19 views

Analyze multiple measurements per subject?

I have 2 subjects. I used to take a single measurement (20 samples) per subject and use a t-test to compare the means. Now I want to add more measurements. I'm going to have 5 measurements per ...
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1answer
20 views

Determine if there is a difference between two large vectors of different sizes of non-normal quantiative data in R

I have two vectors that are of unequal sizes. They contain quantitative data that does not form a normal distribution. I would like to see whether or not they are statistically different. Is there a ...
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38 views

Normality and homogeneity

I have performed certain statistical tests (ANOVA, DMRT, t-test, etc.) assuming my data is normal as well as with homogeneous variance. Now my paper is almost accepted in a reputed journal, reviewer ...
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1answer
68 views

Paired difference t-test vs independent two sample t-test to assess means difference

If I want to compare two sets of measurements, i.e., how much their means differ or how much the sets differ, I would say I have two options: Paired difference t-test: Calculate the differences to ...
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10 views

How many number of items should i include in my test?

I have designed two post test ,a recognition test and a production test.I have inserted 18 items in each test. As I sifted through articles , I 've read that we should include at least 30 items to get ...
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11 views

T-test degrees of freedom

I have just been creating a slide demonstrating a (central interval) confidence band plot using a Neyman construction for a simple standard normal distribution. I created a confidence band plot of ...
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0answers
52 views

Basic methods for detecting outliers

Let $X$ be a matrix of $n$ rows and $m$ columns. $n$ is the number of samples and $m$ is the number of gene expressions. Gene expressions are basically numerical continuous values. Assume we have a ...
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0answers
18 views

Can I compare three averages if no independent variable?

I am not used to this type of data, and am not experienced with statistics so am really getting hung up. This is an undergraduate research project. I have done a total fecal collection on 12 horses. ...
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1answer
15 views

What Statistical Test of Significance is Suited to Comparing Two Classes of Students on Volume of Access?

I'm an educator and I'm delving a little further into stats than I normally would to try to determine how effective a new teaching method is. I'd really appreciate some advice on the best approach to ...
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2answers
13 views

Methods for compiler benchmarking?

In computer science, statistical knowledge is quite low in general. You rarely see standard deviation in papers. Now I am trying to improve at least my skills, but I find myself utterly confused about ...
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1answer
25 views

One-tailed vs. two-tailed t-test and P level

In a two-tailed t-test for a P of 0.1 and a one-tailed test for a P of 0.05, is the t value to show significance the same? I understand that the two-tailed test is looking for significance at either ...
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1answer
23 views

How to compare two Bayesian networks?

I have two different datasets on which I've applied the same learning (K2) algorithm to learn a Bayesian network. I have the conditional probability table (CPT) of the class variable, for each of the ...
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0answers
36 views

Which is the best statistical test for assessing the quality of a prediction?

I have a function that I'm trying to modulate and I would like to have a statistical indicator that inform me how good / poor my prediction is. In the image below, I show the function (...
2
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1answer
28 views

Paired permuted t-tests?

I have a small dataset which are not normally distributed. I would like to perform a pairwise analysis of the differences in values between two groups. It has been suggested that I use permuted ...
3
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1answer
133 views

Significant t-test results accurate or random?

I've performed a bunch of independent t-tests looking for a relationship between 10 different variables in group A and 10 different variables in group B. There seems to be very few significant ...
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1answer
19 views

Comparison of mean values between two periods

An authority has decided to legislate on stricter rules regarding amortization. The previous legislation stated that a mortgage loan has to be amortized down to a degree of at least 75% of the price ...
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0answers
19 views

Multiple T-Test with Trended Data in R

I am having issue getting the p-values from a T-Test for a 'typical trended study'. The aggregated values for satisfaction by months are the following. ...
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0answers
31 views

Independent t test significant but post-hoc planned analysis not

I was analysing two sets of data. In most cases for the study post hoc planned comparisons identified significance (<0.05), however for one sample, this was not achieved. However an independent t ...
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1answer
18 views

paired samples (t-test?) with grouping variable

Im trying to determine the correct analysis for paired data with a grouping variable. I have 3 fish in each of 4 treatments, so 12 fish in total. Treatments are that the fish are fed at one of four ...
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20 views

How to identify items answered differently by some factors such as male vs. female?

I want to do something like this: Variable: students (undergraduate, master students, and PhD students) Research instrument: XXXX (20 items) Reporting: The ANOVA analysis suggested that there is no ...
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1answer
53 views

Testing for mean statistical difference in segments of different length in the same Time Series

I have a Time Series of 336 monthly observations, from January 1987 to December 2014. I'd like to test for differences in uneven (of different size) segments of this time series. In effect, it would ...